Ed Miliband has continued Labour's efforts to win back credibility on the economy by echoing a statement from Ed Balls, the shadow chancellor, that Labour cannot promise to reverse any coalition spending cuts.

In a move to shift the political debate forward, and away from responsibility for the 2010 deficit, Miliband, speaking on the BBC, tried to focus on the tough inheritance likely in 2015, criticising the chancellor, George Osborne, for cutting too fast.

Labour's newly calibrated position is that it opposes some spending cuts, on the basis they slow recovery, but cannot promise to reinstate any of them ahead of an election. The shift comes as polls show a gradual increase in public acceptance of the need for cuts.

Miliband, facing a personal poll slide among Labour supporters, dismissed criticism of his own leadership as "part of the gig".

Balls angered some backbenchers and unions when he said he backed the public-sector pay freeze being continued in the final two years of the parliament by the coalition, on the basis he would put jobs for those out of work ahead of higher pay for those in work.

On the Andrew Marr Show, Miliband said of Balls's remarks: "If Labour was in power now we wouldn't be making those changes. We wouldn't be cutting as far and as fast as the government.

"But when it comes to the next Labour government, if I was saying to you: 'I can absolutely promise to restore this cut or that cut', you would say: 'Well, where is the money going to come for that?'

"This is absolutely responsible opposition. … And it is absolutely the right thing for us to be doing at this stage of the parliament. We are absolutely determined that Labour shows we would be fiscally credible in government."

Miliband's call for a public-sector pay freeze was criticised by the PCS union leader, Mark Serwotka, as "hugely disappointing", and he accused Labour of failing to stand up for "ordinary people".

The general secretary of the RMT rail union, Bob Crow, said Balls was signing "Labour's electoral suicide note". Some leftwing New Statesman bloggers called Balls's move a political disaster.

More broadly, Miliband insisted David Cameron was "coming on to my ground" on issues such as taking on vested interests and "crony capitalism".

"What gives me confidence is that we are winning the battle of ideas. It's not often you say that about an opposition," he said.

"Why is he [David Cameron] coming on to my ground? Because he knows I'm talking about the right issues and the issues that matter to people. That's what gives me confidence."Simon Hughes, the Liberal Democrat deputy leader, criticised Labour's shift, saying: "They can't have it both ways. They can't be hugely critical of the government one day and then say they would have the same policy the next."ends